1. Field of the Invention
The present invention relates to a gas laser oscillator which has a function of judging a start of discharge.
2. Description of the Related Art
In the past, there has been known a gas laser oscillator which stores in advance a ratio of change of a discharge tube voltage relative to a command voltage to the laser power supply when discharge is normally carried out and judges that discharge has started when the difference between this ratio of change and the ratio of change of the discharge tube voltage which is measured when increasing the command voltage becomes within a threshold value. This gas laser oscillator is, for example, described in Japanese Unexamined Patent Publication No. 2011-222586A (JP2011-222586A). In the gas laser oscillator described in JP2011-222586A, the command voltage is made to increase in steps at a first time interval (for example, 0.1 sec to 1 sec) and a pulse-like command voltage (pulse voltage) is superposed over a head part of each step voltage at a second time interval (for example, 10 μsec to 100 μsec).
However, if the pulse voltage is superposed over the step voltage as the command voltage like in the gas laser oscillator described in JP2011-222586A, the current which flows through the laser power supply is liable to overshoot and overcurrent is liable to flow to the power device in the laser power supply. In order to prevent this, it is necessary to gradually increase the command voltage until start of discharge is judged. Therefore, a relatively long time is required for shift from a laser standby state to a laser working state.